If this property returns an empty string (""), there is no operation available to reapply to the control. You can use this method to determine the last action undone in the System.Windows.Forms.RichTextBox control that can then be reapplied to the control when a call to the RichTextBox.Redo method is made. You can determine whether there are any operations to be reapplied to the control by using the RichTextBox.CanRedo property.